Well I wouldn't and why would you want to?

The only safe colorants are red ochre (iron oxide), yellow ochre( a mixture of iron hydroxide and iron carbonate), and some forms of carbon black (esentially charcoal dust--avoid petrochemical soots!). All others are either poisonous aniline dyes (think RIT fabric dye), or toxic metal salts or oxides. A very few brands might use vegetable dyes or food colorings, but those fade very quickly. If you have a pile of it that you want to use up, I suggest you keep it far, far away from vegetables or fruit trees!